Phagocyte killing of Campylobacter jejuni in relation to oxidative activation

When studying the interaction between Campylobacter jejuni and human neutrophils, we found that four different clinical isolates showed a great variability in this association. Also the ability to induce neutrophil production of oxidative metabolites, measured as chemiluminescence (CL), differed between the strains. Surprisingly, strain 1, which showed weak interaction with neutrophils and high resistance to killing, induced the highest CL response. All strains evoked an intracellular CL response, and three strains also gave rise to an extracellular response. This extracellular release of toxic oxygen species might contribute to the local tissue damage during infection. There was no clear correlation between association, killing and oxidative response. However, one strain that only evoked an intracellular generation of oxygen metabolites also showed the highest sensitivity to killing. Phagocytosis was increased up to ten times after opsonization with normal human serum. The intracellular CL production increased several fold, whereas the extracellular generation of oxygen species disappeared or was considerably decreased after opsonization. These results indicate that complement-opsonized C. jejuni are phagocytosed and readily attacked by the oxidative defence system within the phagosome.